R programming

AGENDA
• History and evolution of R
• Principle and software
paradigm
• Description of R interface
• Advantages of R
• Drawbacks of R
• So why use R?
• References for learning R

R has developed from the S language
HISTORY AND EVOLUTION OF R
S Version 1
S Version 2
S Version 3
S Version 4
Developed 30 years ago for
research
applied to the high-tech industry

99 ’s:ϭ Ϭ R developed
concurrently with S
1993: R made public
The regular development of R
Acceleration of R
development
R-Help and R-Devl mailing-lists
Creation of the R Core Group
Source: R Journal Vol
1/2

Growing number of packages
2001: ~100 packages
2009: Over 2000
packages
Source: R Journal Vol
1/2
2000: R version 1.0.1
Today: R version
2.14

Explosion of R popularity in the last decade
 Object-oriented, growing user base, scripting
features
 Free and open-source
 Irrational reasons: R seen as « cool »

Comparison of Mailing Lists
HISTORY AND EVOLUTION OF
R

Popularity amongst programming languages
HISTORY AND EVOLUTION OF
R

Number of Blogs
Data as on Mar
2012
Software Number of Blogs
R 365
SAS 40
Stata 8
Others 0-3

AGENDA
• History and evolution of
R• Principle and software paradigm
• Description of R
interface
• Advantages of R
• Drawbacks of R
• So why using R?
• References for learning R

 R is rather a programming language
 Limited user-friendly interfaces for data analysis
 Is object oriented and almost non declarative
 Similar to programming languages like Fortran, C, Java,
Python
R is not really a (statistical) software
PRINCIPLE AND SOFTWARE
PARADIGM

Recent endeavours to enhance R user-
friendliness Several GUIs in development
R-commander
RKWard
Rattle
R has limited Graphical User Interface (GUI) options
PARADIGM

R Commander (RCmdr)
PARADIGM

RKWard
PARADIGM

Rattle
PARADIGM

Inherent limitations of pervasive Excel-like spreadsheets
PARADIGM
VS.

Sophisticated but costly SAS
PARADIGM
VS.

AGENDA
paradigm• Description of R interface
• Advantages of R
• Drawbacks of R
• So why using R?
• References for learning
R

R console
DESCRIPTION OF R INTERFACE
R desktop
shortcut
RGui: R basic
interface
R command
line (space to
write
instructions)

Using the command line in R console
First false
sentence followed
by R’s error
message
Second correct
sentence
Declaration and
printing of the
sentence as a R
object
Simple math
computations
Basic information
about the R object
containing the
sentence

RGui menu: File tab
File tab: Usual
basic and general
operations

RGui menu: Edit tab
Edit tab: basic
and general
editing
Results of
the
data editor
Data editor:
entering the
oďjeĐt’s
name

RGui menu: View tab
View tab:
viewing Toolbar
and/or Status bar

RGui menu: Misc tab
Misc tab:
diverse
operation
s

RGui menu: Packages tabs
Packages tab:
adding functions
to R foundation

RGui menu: Windows tab
Windows tab:
usual options
to arrange the
tiles

RGui menu: Help tab
Help tab: very
important
links to help

AGENDA
paradigm
• Description of R interface• Advantages of R
• Drawbacks of R
• So why using R?
R

 Open source code
 You can access the code of the
software
 In-depth understanding of what R does
 Modify the code
ADVANTAGES OF R
Adress of the
« mgcv » package
Link with Package sources (.tar.gz file)
Screenshot of the CRAN webpage of the « mgcv » package. Source: CRAN

R access to source code
ADVANTAGES OF R
Screenshot of unzipping the « mgcv » package and browsing through the package’s
files.
Unzipping
mgcv_1.7-
13.tar.gzfile (with 7zip)
List of
directories in the
« mgcv »
package
List of functions (i.e
open code) in the « src
» (i.e code sources)
directory the « mgcv »
package1 2 3

R is free
ADVANTAGES OF R
Software Academics Demo Commercial
(basic)
Commercial (full)
R Free Free Free Free
SAS Free to $100s Not available $1 000s $10 000s
Statistica $100s 30 days limit ~$1 000 $10 000
Excel
(Microsoft)
Free to $10s Limited ~$100 $100s
SPSS (IBM) $100s 14 days limit ~$2 000 $1 000s

Interface with other languages and scripting capabilities
ADVANTAGES OF R
Interfaces with virtually any other programming language
Fortran, C, C++, Python…
Tailor or rewrite your old codes in R
R as a scripting language
R scripts can launch or be launched by other languages
« mgcv.c » file in the
« mgcv » package coded in typical C programming language
Screenshot of the file « mgcv.c » of the « mgcv » package open in WordPad

R visualization capabilities
ADVANTAGES OF
R

 R ~ tool used by the finest
researchers
 Top-notch analytics capabilities
R role in academia
ADVANTAGES OF R

Free open source philosophy
To summarize
ADVANTAGES OF R
 R websites with many
examples
 Free books
 Free online open courses
 Twitter accounts
Online help and discussion
 Mailing-lists
 Very active and diverse forums
 Communities of developers and
helpers

AGENDA
paradigm
• Advantages of R• Drawbacks of R
• So why using R?
R

Poor management of large datasets
Avoid imbricated loops
Prefer R advanced language for data structure
Complicated structure of packages in R
 Dozen of packages
 To be loaded every time in memory
R packages to better manage memory
 Rhadoop (inspiration from Google)
 Ff
 bigmemory
Average memory performance
DRAWBACKS OF R

No default parallel execution
R packages to use several cores
Top skills needed for high performance computing
A high-level programming language
Abstract and modern (Python…Ϳ
More productive coding
But further from « machine language »…
… meaning 100 times slower than C
Average computing performance
DRAWBACKS OF R

Difficult to inspect data
sets
Difficult data visualization and management
DRAWBACKS OF R

Problems for large organizations
R made of several thousands independent packages
No deployment plan for complex organizations
No installation support
Lack of code accountability
Thousands of individual independent R developers
Nobody responsible for the quality of the code
Potentially high hidden costs with R
 Total cost may favour commercial solutions for complex computations made in
large
corporations
Difficult architecture management
DRAWBACKS OF R

Steep learning curve
R code far from undergrad computer science courses
Very complex data structures (useful if mastered)
Is R’s syntax not logical?
Relatively difficult to learn
DRAWBACKS OF R
Still, not more difficult to learn than
SAS


Both SAS and R more abstract than basic programming languages (Fortran, C…
Ϳ Difficult to learn = more rewarding professionally!!

AGENDA
paradigm
• Advantages of R
• Drawbacks of R• So why use R?
R

No language is perfect!!
Contradictory objectives to meet
Strengths and weaknesses of each language
Effect of legacy and the culture of the organization
Use existing solutions (system architecture, BA tools…Ϳ
Habits in business analytics
Different needs imply different tools
Large corporations + defined procedures  SAS-like
Less financial resources + quick proof of concept  R
More positive than negative points
SO WHY LEARN R?

Very appealing solution
SO WHY LEARN R?
Popularity of business analytics software (green = very popular, red = unpopular).
Over
all
Corpor
ate
Consulta
nts
Academ
ics
NGO/Go
v'tR SAS
IBM
SPSS
STATIST
ICA
Own
code

AGENDA
paradigm
• Advantages of R
• Drawbacks of R
• So why using R?• References for learning R

Many books available: choose the one that fits you!
Style, pedagogy, theory vs practice
Browse several books at local library or store
Springer’s UseR! Series
(http://www.springer.com/series/6991)
Recent, concise, good quality, affordable, diverse
Pure rookies: « A beginners’ guide to R », « R by example »
One step forward: « Business analytics for managers »
Intensive Excel users: « R through Excel »
O’Reilly R series ;for programmersͿ
« R cookbook », « R in a nuttshell »
Books
REFERENCES FOR LEARNING R

Websites
R official websites
The R project for statistical computing (www.r-project.org )
Mailing lists (« R-help », Special Interest Groups) and R journal
Official (austere) manuals (« An introduction to R »)
Other websites
UCLA online R resources http://www.ats.ucla.edu/stat/r/)
R blogs aggregator (www.r-bloggers.com)
Social networks: LinkedIn groups (The R project for statistical computing), Twitter accounts
(@RevolutionR, @inside_R), jobboards

Growing number of conferences about R Official International R UseR! conference
Annual during a few days in new venue (Google it!)
Lots of materials about many topics
Other conferences or venues
 Find (or even start!) a R user group close to your location (R Wiki geographical list, map
ofgroups on « meetup.com »)
 Events and news from R-bloggers blog
Conferences

R programming

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R programming